A novel PDE10A inhibitor just showed safety and efficacy in a large Phase 2 trial for acute schizophrenia. 👏
📌 PDE10A inhibitors represent a non-dopaminergic approach—targeting phosphodiesterase 10A to modulate both D1 and D2 pathways indirectly. This could be a game-changer for patients who don’t respond to or can’t tolerate traditional D2 blockers.
🔍 The trial demonstrated: ✅ Significant reduction in PANSS total scores ✅ Favorable side effect profile (no EPS or prolactin elevation) ✅ Oral formulation, once daily
This reinforces the urgent need to diversify our treatment mechanisms beyond dopamine antagonism. As treatment-resistant schizophrenia remains a major challenge, we’ll take all the innovation we can get.
🧠 Stay tuned—PDE10A could join the ranks of TAAR1 agonists and muscarinic agents in reshaping how we treat serious mental illness.
There is limited high-quality randomized controlled trial (RCT) evidence specifically comparing Zyprexa (olanzapine) or Seroquel (quetiapine) for the treatment of stimulant-induced psychosis (SIP), including cocaine-induced psychosis. However, some RCTs and observational studies provide useful insights:
Olanzapine (Zyprexa)
RCT Evidence:
A 2022 meta-analysis of antipsychotic treatments for stimulant-induced psychosis included olanzapine and found it to be effective in reducing positive psychotic symptoms, often comparable to haloperidol but with a better side effect profile (less extrapyramidal symptoms) 11.
A double-blind RCT comparing olanzapine vs. haloperidol in methamphetamine-induced psychosisfound that both were effective at reducing PANSS (Positive and Negative Syndrome Scale) scores, but olanzapine was associated with better tolerability 22.
Another RCT in methamphetamine-induced psychosis compared olanzapine and risperidone, showing similar efficacy but better tolerability with olanzapine 33.
Quetiapine (Seroquel)
RCT Evidence:
A small RCT in methamphetamine-induced psychosis found that quetiapine was effective but tended to require higher doses to achieve symptom resolution 44.
A retrospective study on cocaine-induced psychosis suggested that quetiapine may help reduce symptoms, but data is weaker compared to olanzapine or risperidone 55.
Quetiapine has also been studied as an option for reducing cocaine cravings, but results are mixed and it is generally less preferred for acute agitation compared to faster-acting options like olanzapine.
Head-to-Head Comparison
There is no direct RCT comparing olanzapine vs. quetiapine for stimulant-induced psychosis, but based on available data:
Olanzapine is generally preferred for acute agitation and psychosis because of its faster onset and greater D2 blockade.
Quetiapine may be useful in milder cases or for individuals needing sedation, but higher doses are often required.
Clinical Implications
For acute stimulant-induced psychosis, olanzapine (5–10 mg IM or PO) is a common first-line option due to rapid onset and favorable side effect profile.
Quetiapine (200–400 mg PO) can be considered, particularly for patients needing sedation or those with comorbid conditions like bipolar disorder.
Other antipsychotics with strong evidence include risperidone and haloperidol (though the latter has more extrapyramidal risk).
After reviewing the available literature, direct randomized controlled trials (RCTs) comparing olanzapine (Zyprexa) and quetiapine (Seroquel) for stimulant-induced psychosis (SIP), including cocaine-induced psychosis, remain scarce. However, some studies provide relevant insights:
Olanzapine (Zyprexa):
Efficacy: A randomized, double-blind trial compared olanzapine and haloperidol in patients with amphetamine-induced psychosis. Both medications effectively improved psychotic symptoms in the short term, with olanzapine showing a faster onset of action.
Quetiapine (Seroquel):
Efficacy: A double-blind RCT compared haloperidol and quetiapine for methamphetamine-induced psychosis. While both medications reduced psychotic symptoms, quetiapine appeared to have a more favorable profile in reducing certain symptoms over time.
Indirect Comparisons:
First-Episode Psychosis: A 52-week randomized, double-blind study evaluated olanzapine, quetiapine, and risperidone in early psychosis patients. All three antipsychotics demonstrated comparable effectiveness, as indicated by similar rates of treatment discontinuation.
Conclusion:
While direct RCT evidence comparing olanzapine and quetiapine specifically for stimulant-induced psychosis is limited, existing studies suggest that both medications are effective in managing such conditions. Olanzapine may offer a faster onset of symptom relief, whereas quetiapine might present a more favorable side effect profile. Clinical decisions should be individualized, considering factors such as patient history, specific symptomatology, and potential side effects.
In my practice, I see many patients who have been on high doses of antipsychotics for extended periods, particularly first-generation antipsychotics, which carry a higher risk of developing tardive dyskinesia (TD). While two FDA-approved treatments for TD exist, their high cost and limited availability can make access challenging in community mental health settings. This has led me to explore alternative treatments like amantadine. Like many of you, I wanted to understand the evidence supporting its use, so let’s take a closer look at what the research says about amantadine as a treatment option for TD.
The evidence for the use of amantadine in treating tardive dyskinesia (TD) has been explored in several small randomized controlled trials (RCTs), though it remains limited compared to other treatments.
Efficacy of Amantadine: Some studies suggest that amantadine, an NMDA receptor antagonist, may offer mild to moderate improvement in TD symptoms by modulating dopaminergic pathways. For instance, an early RCT (2007) tested amantadine in schizophrenia patients with TD and reported some improvements in abnormal involuntary movements compared to placebo. However, the sample size was small, and results were modest.
Comparative Effectiveness: Few trials directly compare amantadine to other TD treatments like VMAT-2 inhibitors (e.g., valbenazine, deutetrabenazine), which are the preferred treatment options due to stronger RCT evidence. Amantadine’s effects may be less pronounced, though some patients have reported partial symptom relief, especially when TD is not severe.
Safety Profile: In RCTs, amantadine is generally well-tolerated in TD patients, with few serious side effects. However, common side effects include dizziness, insomnia, and gastrointestinal issues, which may limit its use in certain patients, particularly those with cognitive or movement comorbidities.
Overall, while RCTs support some benefit of amantadine in TD, the effect size is generally moderate. VMAT-2 inhibitors are preferred based on stronger, more consistent RCT data, although amantadine may still be considered for patients who cannot tolerate or do not respond to these primary therapies.
Antipsychotic Drugs and Cognitive Function: Key Findings from a Systematic Review and Meta-Analysis
Background: Cognitive impairment is a core feature of schizophrenia, often leading to significant functional disability. Antipsychotic medications are the main treatment for schizophrenia, but their impact on cognitive function remains debated.
Objective: This systematic review and network meta-analysis aimed to compare the effects of different antipsychotic drugs on cognitive function in patients with schizophrenia.
Methods: The review included randomized controlled trials (RCTs) that assessed cognitive outcomes in patients with schizophrenia treated with antipsychotics. A network meta-analysis was conducted to compare the cognitive effects across different antipsychotic drugs.
Key Findings:
Cognitive Improvement:
All antipsychotics studied showed modest cognitive benefits, though the effect sizes were small.
Second-generation antipsychotics (SGAs) generally performed better than first-generation antipsychotics (FGAs).
Among SGAs, lurasidone and amisulpride demonstrated the most pronounced cognitive improvements.
FGAs like haloperidol showed the least benefit for cognitive function.
Domains of Cognitive Improvement:
The drugs improved different cognitive domains, including working memory, processing speed, and executive functioning, though no single drug showed superiority across all domains.
Comparative Effectiveness:
In head-to-head comparisons, lurasidone and amisulpride were consistently ranked higher for cognitive improvement.
Olanzapine and risperidone also showed beneficial effects, though to a lesser extent.
Adverse Effects and Tolerability:
Cognitive improvements were often seen alongside side effects, with some drugs (e.g., olanzapine) associated with metabolic risks that may counterbalance cognitive benefits.
Limitations:
The analysis emphasized the small effect sizes, suggesting that while antipsychotics may slightly improve cognition, the changes may not be clinically meaningful in many cases.
Cognitive rehabilitation therapies may need to be paired with pharmacological treatment for more significant cognitive gains.
Conclusions: While antipsychotics can modestly improve cognitive function in schizophrenia, the benefits are relatively small, and no drug significantly outperforms others across all cognitive domains. Lurasidone and amisulpride may offer the greatest cognitive benefits, but additional interventions may be necessary to address cognitive deficits effectively.
It wasn’t that long ago when I was sitting in lectures as a first-year psychiatry resident. I learned about the first- and second-generation antipsychotic medications in detail. One commandment that was always preached in my training was to never combine two antipsychotic medications because there is no additional benefit. Today we are here to explore this idea and see if there is truly no additional benefit to using two antipsychotics and explore why there is so much antipsychotic polypharmacy in serious mental illness.
Since most guidelines discourage the use of multiple antipsychotic medications, why are many psychiatrists going against these guidelines? In most cases we are just trying to stabilize patients, get them better, and keep them out of the hospital as the goal is to provide most psychiatric care in the community. To reach these goals a single medication does not always produce the desired results.
Patients that end up on multiple antipsychotics have some unique characteristics. They tend to have more severe psychotic symptoms, are male, unemployed, and younger. Those with frequent inpatient admissions on involuntary status are also more likely to end up on two medications.
What To Do When a Single Medication Is Not Enough?
The use of multiple antipsychotics is an area of limitted research. However, there is a difference between rational polypharmacy and irrational polypharmacy.
We should start this discussion by saying a patient should be started on monotherapy titrated to an effective dose and continued on the medication for 6 weeks prior to making a change. If the first medications fails, then switching to another medication or long acting injectable is a reasonable next step. If after another 6 weeks of treatment the patient remains unstable and symptomatic the technical next step is to start clozapine. There are many reasons why clozapine may not be a good option for a particular patient including the strict requirements for weekly complete blood cell counts CBCs.
Assuming this process is followed and the patient is still symptomatic what’s the next step?
Consider Receptor Binding Profiles
This is the first step in prescribing two medications rationally. Most first-generation medications such as Haldol will bind tightly to D2 receptors and stay bound to the sites longer. Second-generation medications like quetiapine are known to bind to the receptors and quickly dissociate giving an on-off like effect. Tight binding and longer duration of binding can lead to extrapyramidal side effects (EPS), whereas quick on-off medications like quetiapine have limitted EPS risk.
You should also consider other receptors the medication may target such as histamine and muscarinic cholinergic receptors. It would be best to avoid combining two medications that have high antihistamine and anticholinergic activity.
Let’s look at some scenarios where antipsychotic polypharmacy makes sense.
Patients With Acute Agitation
This is a common problem on the inpatient unit. A patient is on a low-potency quick on-off medication like quetiapine but remains symptomatic and is engaging in dangerous behavior.
The addition of a higher potency, higher affinity medication like Haldol makes some sense here. This will control the acute agitation, can be titrated until the psychotic aggression is controlled, and can be stopped as soon as the patient is stable on quetiapine. We can see how the receptor binding profile makes this combination reasonable.
Clozapine Refractory Patients
What do you do when a patient is on the best antipsychotic medication but remains symptomatic?
We do have several lines of evidence that we can look at for this question. One option is to add low dose risperidone. This is a similar idea to adding Haldol to quetiapine. Clozapine has lower affinity for the D2 receptor than risperidone which has much higher affinity for D2 receptors. There were two placebo-controlled trials that support this combination. Before combining medications, I would suggest obtaining a clozapine level to make sure it’s therapeutic.
There are two more recent studies that compared multiple antipsychotic medication combinations and used rehospitalization as a measure of effectiveness. Both studies found a significant reduction in rehospitalization for patients receiving polypharmacy compared to those receiving monotherapy. The best outcome was achieved when clozapine was combined with aripiprazole.
Patient is On a Long Acting Injectable (LAI) but Remains Symptomatic at the Highest Dose
This is a common problem because the doses of LAIs are limitted. For example, the LAI aripiprazole (Aristida) is limitted to a maximum dose of 20 mg/day. The oral formulations of aripiprazole allow for a maximum dose of 30 mg/day. One strategy is to give the injection early. This will usually be done on week 3 for formulations that last 4 weeks. Another option is to add another medication with a different receptor binding profile such as the clozapine aripiprazole combination that was shown to reduce the risk of rehospitalization.
Treatment of Insomnia
The addition of low dose quetiapine to a medication like paliperidone is common in clinical practice. Once D2 receptor blockade has been maximized by reaching an effective dose of paliperidone, considering the addition of as need (PRN) quetiapine for its low potency and sedating properties is reasonable. The medication should be used PRN only and should be removed once the insomnia has resolved. Consider a sleep study if sleep apnea is possible and using other options such as short-term orexin antagonists, melatonin, and sedating antidepressant if appropriate.
Treatment of Antipsychotic Induced Side Effects
I know what you are going to say, adding a medication to treat a side effect of another medication doesn’t make sense. Let’s take an example to illustrate why this makes sense. If a patient is stable on risperidone and is discovered to have an elevated prolactin level you have an obligation to address it. The addition of low dose aripiprazole has been proven to reduce prolactin levels in these cases. Another possibility is using aripiprazole to reduce the metabolic burden of medications such as clozapine. There is much more limited data in this area and I would consider metformin a much better option to start with if antipsychotic induced weight gain is a problem.
In the process of Switching Medication the Patient Achieves Remission
This is another common clinical scenario. A patient didn’t respond to a medication, and you begin decreasing the dose of the first medication while titrating the new medicine. Then suddenly they are better. You don’t know why but they are better than they have ever been and now you are afraid to make any additional changes. Ideally you would finish the process and appropriately titrate the new medicine while discontinuing the ineffective medication. There is no good data to support inadequate dosing of two antipsychotics, and it’s best to continue your taper/titration and reevaluate after it’s complete.
Conclusion
There is still limited data to support the use of multiple antipsychotic medications although it is often seen in clinical practice. There are a few places where the addition of a second medication makes sense, and we can use receptor profiles to help us make rational decisions and avoid excess side effect burden.
I get a lot of questions about the risks and side effects associated with antipsychotic medications. These medications are no longer used exclusively in schizophrenia, and they are now widely accepted as treatment for bipolar disorder, adjunctive therapy for depression, and even severe anxiety disorders resistant to other medications.
As a result, more people than ever are being prescribed these medications and many are concerned about the risk of side effects. One that I get asked about all the time and maybe the most feared of all side effects is the often-irreversible movement disorder called tardive dyskinesia (TD).
This discussion and video will help you understand the risk of developing TD and the approaches to managing it should symptoms develop.
EPS and Dopamine Blockade:
Dopamine receptor blockade can cause a variety of movement disorders, after all dopamine is directly involved in the process of movement. We call the movement disorders associated with dopamine blocking medication extrapyramidal syndromes (EPS).
Most EPS develop shortly after staring medication and are treatable with medication and stopping the offending agent. This is not the case for TD. There is a delay in the onset of symptoms (tardy) and persistence of the symptoms well after the medication has been stopped.
TD can develop after medication is used for a few months, or as little as a few weeks in the case of elderly patients. TD can also occur when a medication is discontinued or reduced.
Myths About TD:
The longer you stay on an antipsychotic the more likely you are to develop TD. The prevalence (proportion of people who have a condition at or during a particular time) of TD increases with time, but the incidence (number of new cases) decreases with time.
With first generation dopamine blockers 40-50% of patients developed TD but not in a linear fashion. Half of the patients developed TD within the first 5 years of taking medication. The incidence is about 5% per year over the first 5 years and then the incidence decreases to 1-2% per year and levels off after that.
TD is more likely to occur in the first few years of treatment and less likely after 5 years of treatment.
The risk of TD does not increase if acute EPS occurs and does not decrease if no acute acute EPS develops
Risk factors for the development of TD:
Diagnosis of schizophrenia
Older age
Female sex
Schizophrenia itself causes TD and has been described in the literature long before medications were used as treatment. The prevalence was lower about 5-10% Vs 40% seen after medications were used in treatment. This occurs because schizophrenia is not just a disease of the cortex it also involves the basal ganglia which is responsible for the movement disorders.
TD Risk at 1 Year of Treatment:
Risperidone 0.6%
Olanzapine 0.5%
Haloperidol 2.7% to 4.5%
It’s clear from this data that first-generation dopamine blocking medications have a much higher rate of TD compared to the second-generation medications. This 0.5% rate is similar to the rate seen in the natural course of illness in schizophrenia (essentially the same as placebo).
In patients with mood illnesses who use dopamine blocking medications there are very low rates of TD. It can occur in mood disorders but it’s very infrequent and does not occur at nearly the same rates seen in schizophrenia.
The risk of TD is associated with the underlying pathology of schizophrenia which is distinct from other mood disorders.
Treatment of TD:
For a long time, there was no treatment for TD. In the last few years two medications have been developed Valbenazine (ingrezza) and deutetrabenazine (Austedo) both of which are FDA approved.
The mechanism of action of these two medications is VMAT-2 inhibition. Vesicular monoamine transporter 2 inhibition results in decreased monoamine activity at the synapse.
The studies used to gain FDA approval of these medications showed a mild improvement on the abnormal involuntary movement scale of 2-3 points in patients with mild TD.
It’s important to keep in mind TD did not go away fully but it did improve over placebo.
The best treatment for TD is to stop the dopamine blocker. In some cases, if the dopamine blocker is stopped early enough TD is reversible. In many cases the medications are continued because there are no other clinical options and you are left with treating TD with VMAT-2 inhibitors.
